在 Android 中，ClipData 中的“ label”参数到底是什么？

根据 Android 文件，ClipData 使用“标签”作为复制数据的一种表示形式。

ClippedData 是一种包含一个或多个 Item 实例的复杂类型，每个实例都可以保存数据项的一个或多个表示形式。为了向用户显示，它还有一个标签和图标表示。

然后它进一步解释“标签”作为 剪辑数据的用户可见标签在一些 API 文件。然而，我仍然对标签的用法感到困惑。

用户如何看到这个标签？我该怎么用？当我调用 ClipData 工厂方法 newPlainText(CharSequence label, CharSequence text)时，我应该为这个标签设置什么？例如:

private void copyToClipBoard() {


ClipboardManager clipboard = (ClipboardManager) getSystemService(CLIPBOARD_SERVICE);
ClipData clip = ClipData.newPlainText(
"text label", // What should I set for this "label"?
"content to be copied");
clipboard.setPrimaryClip(clip);
Toast.makeText(AboutActivity.this, "Saved to clip board", Toast.LENGTH_SHORT).show();
}
23348 次浏览
小开
最佳答案 
ClipData clip = ClipData.newPlainText(
"text label",
"content to be copied");

here text label describes what data is in clip

eg. 

ClipData clip = ClipData.newPlainText(
"user Name",
user.getName());

we can retrive this by using

clip.getDescription ();
小开

It seems like the "User-visible label for the clip data" description in the documentation should be interpreted as something you as a developer can set and then show to the user yourself and not as something that the Android system will show to the user.

When looking at the Android source code the ClipDescription.getLabel() method seems to be unused before Android 5.0. In 5.0 RemoteInput, RemoteInputCompatJellybean and com.android.mail.compose.ComposeActivity stated using the method.

If you look at the usage all these set a label that is not meant to be seen by the user but instead used to programatically identify the clip at a different place in the code.

When looking at how ClipData.newPlainText() is used within Android, most of the time null is given as label, suggesting the label is not really used for anything.

It is of course possible that some phone manufacturer or some other app developer takes the label and displays it to the user in some situation. But in general it should be safe to assume that the label of a clip will only be shown to the user in your app if you show it yourself.

小开

Today while working on my app I discovered one use case for ClipData label. Some apps set it to null while other apps use it pretty much.

In the case of my app I am listening to the ClipManager's addPrimaryClipChangedListener

I am doing this in a service class that runs in the background almost all the time. I want to treat data added to the primaryClip from within my app different from data added in another app (lets say text copied in a web browser).

Here is an extract of my code and how I am using ClipData label:

mClipBoardManager.addPrimaryClipChangedListener(new ClipboardManager.OnPrimaryClipChangedListener() {
@Override
public void onPrimaryClipChanged() {
String clipLabel = "default";
if (mClipBoardManager.getPrimaryClip().getDescription().getLabel() != null) {
clipLabel = mClipBoardManager.getPrimaryClip().getDescription().getLabel().toString();
}
if (clipLabel.equals("auto_copy_text")) {
//TODO: Text from my app do stuffs you will do with text from my app
} else {
//TODO: Text from some other app
}


}
});

In my app when I am adding data to primaryClip I include the label like this:

private void addToClipboard(String text) {
mClipboardManager = (ClipboardManager) getSystemService(CLIPBOARD_SERVICE);
mClipboardManager.setPrimaryClip(ClipData.newPlainText("auto_copy_text", text));
}

I hope this helps

小开

One more thing I noticed is that if users copy data with the same label again then previous text with the same label will be overwritten. So one label can keep only one copy of data & will be helpful in clearing the previous clutter. Also label can be used for identifying your unique text & can be used to retrieve your text data even if its the not last thing user copied.


提交答案